Wow you are in for one big nasty pain in the butt job! I do this stuff for a living and I avoid replacing oven liners if at all possible. Not something I'd recommend for a novice. But if you must.........with the unit out of the wall and sitting on the floor, Start by taking the doors off if you haven't already. Then take off the back panels. Disconnect the oven sensor, broil & convection element wiring then remove them from inside the oven. Remove the convection fan blade (the nut is a reverse thread!) The hidden bake element most likely won't have to be removed. Look for any screws on the back of the oven holding the liner in and remove them. Remove the oven vent tube from inside the oven. This should turn about a quarter turn counter clockwise then pull out. Remove the light housing(s). They should have a disconnect plug when you pull the housing out but the plug may be all the way at the back of the oven & you will have to pull the wire through. Now you've done all of the "easy" stuff. Depending on how this one is made, you may or may not have to remove the front frame. Look at the front of the oven opening to see if the liner overlaps the frame or sits behind it. If behind it, start disconnecting every screw you can find on the sides and front holding the frame in. Last, sometimes there are one or a few screws inside the oven cavity near the front holding it in, if so remove them. Now once that is done or if you did not have to do that step, CAREFULLY start wiggling out the liner. The part thats difficult here is getting the liner out without disturbing the insulation. It may help to lay the oven on its back at this point so when you get the liner out the top of the insulation does not fall down. If you are still doing ok at this point, congratulations! Now all you have to do is reverse those steps! Depending on where the oven light is mounted you may have to fish the wires back through so at this point it might help to put a string or another wire through the hole to pull the wires through.
Now if any of these instructions sounds scary to you, don't ruin your $2000+ oven, call a professional. It might cost you a few hundred dollars but might save you a lot of trouble and aggravation!